Dr Hector Perera       London

When we cook, sometimes we cook water based foods directly on the fire and sometimes we fry. We fry fish or stakes or even papadams, sprats and red chilies. I know fried red dry chilies are too hot to eat but a taste of it is very appetising. One cannot help to avoid any cooking fumes from the frying pan when we fry those things but try and avoid the cooking fumes from your frying pan, especially if the ventilation is poor. People in hot weather countries like in Sri Lanka always cook and fry with open windows in the kitchen but in cold weather countries such as in Canada and England, most of the times they depend on the extractor fans for ventilation.

Your Saturday night steak might not taste quite so good after you read this article or you might think more carefully about how you prepare it and perhaps consider replacing your ventilation fan.

Research evidence

NTNU researchers have now documented what has long been suspected: The fumes from normal cooking contain both tars and high amounts of chemical compounds called aldehydes. Both can cause cancer.

According to Andres Fullana , Angel A. Carbonell-Barrachina ,^§ and Sukh Sidhu at Environmental Engineering, University of Dayton, 300 College Park, Dayton, Emissions of low molecular weight aldehydes (LMWAs) from deep-frying of extra virgin olive oil, olive oil, and canola oil (control) were investigated at two temperatures, 180 and 240 °C, for 15 and 7 h, respectively. The oil fumes were collected in Tedlar bags and then analyzed by gas chromatography−mass spectrometry. Seven alkanals (C₂−C₇ and C₉), eight 2-alkenals (C₃−C₁₀), and 2,4-heptadienal were found in the fumes of all three cooking oils. The alkanals are nothing but aldehydes with a R-CHO structure. The R group is attached to the carbon of C=O group then the carbon of C=O has a H atom attached then it becomes an aldehyde. The R group can be with one or more carbon atoms. The generation rates of these aldehydes were found to be dependent on heating temperature, showing significant increases with increases in temperature. The LMWA emissions from both kinds of olive oils were very similar and were lower than those observed from canola oil under similar conditions. These results suggest that frying in any type of olive oil, independent of its commercial category, will effectively decrease the generation of volatile aldehydes in the exhaust. This fact is important because less expensive refined olive oil is usually used for deep-frying operations, whereas extra virgin olive oil is usually used as salad dressing.

Ventilation is very important in cooking

The results were unambiguous. We don’t recommend the fans fitted with carbon filters, because they absorb only large particles and spew the small ones back. The results were better when the fans vented directly to the outside, and the best results came when the fans were placed between two walls, between two cupboards or up to a corner.

This helped to increase suction. It is also very important to let the fan run for fifteen minutes after you’re done cooking,” say project manager Kristin Svendsen and PhD candidate Ann Kristin Sjaastad.

Unhealthy chemicals in cooking fumes

The chemicals that they were particularly interested in were polycyclic aromatic hydrocarbons (PAH), which have been found in the fumes from different types of cooking oil.

The researchers explain that the International Agency for Research on Cancer (IARC) has recently classified the fumes from high-temperature frying as ‘probably’ cancer-causing to humans. They also highlight the results of a 1986 study that reported an increased risk of respiratory tract cancer in cooks and bakers. The researchers say that although there is limited evidence” from studies in humans that emissions from high-temperature frying are carcinogenic, animal experiments have provided sufficient evidence” to suggest that there is a link.

How do you like British TV chefs cooking?

Sometimes I watch some of the cooking programmes in British TV and noticed that quite often the chefs fry carelessly. Fumes all over the studio and even the guests start coughing and sneezing because of those smelly gases. It is possible they are in a hurry to show the audience the method of cooking and frying so they fry rush rush giving out fumes all over. Frequently they just toss the food in the air for a couple of times then say, Cooked”. When the so called cooked beef is cut, you would notice nice red colour. That means beef is not evenly cooked.

British TV chefs must set an example

I think those British TV chefs must cook and fry carefully so that the children who watch the show might follow their type of cooking. They might think that must be the correct way to cook and fry otherwise why did those type of cooking are allowed to be shown to the public in TV? I have my doubt if they have any scientific ideas in cooking and frying. I regard the kitchen is the chemistry laboratory of the home. We always deal with nothing but chemicals in the kitchen.

High temperature cooking and frying

Deep frying cause hydrogenation of the unsaturated vegetable oil, turns it into trans-fats. Trans-fat increases the risk of having heart diseases, cancers, and many other chronic diseases. This term cis and trans refers to the position of other groups attached to the C=C double bond of the fats. If the groups are on the same side of the C=C bond then they are considered as cis then if the groups are on the opposite side of the C=C double then they are called in trans position.

Most people are careless in handling the fire in cooking and frying, they just turn the gas knob to the maximum so the temperature it gives out is very high. Scientists have found that high temperature cooking and frying are unhealthy because the high temperature decomposes the oil and other chemicals. In the case of oils, you may start with cis type of oils but due to high temperature, it becomes trans type which is totally unhealthy. As mentioned above the trans fat causes so many diseases such as heart diseases, cancer and many more chronic diseases.

 Have you noticed in take away joints the slices of fish (fillets), coated with batter are fried in large containers filled with boiling oil. I have already mentioned that high temperature decomposes the oil. Frying in such oil destroys all nutritious values of the fish except the unique taste.

Then frying potato chips in the same oil will certainly destroy the nutritious values including the vitamins in the chips. It is also a known that the brownish colour produced in frying starchy foods emanates a cancer producing chemical called ‘Acrylamide”. People in Canada and England frequently eat fried food and also BBQ or barbecued food. I know it for fact they taste nice but the doctors say they are unhealthy. I am sure an occasional treat in moderation would not do any harm but some people eat frequently on daily basis or even as their weekend treats. When the sun is out in the summer in Canada and England, some people cannot wait until they eat BBQ. They invite some friends and relative for the BBQ treat that means they share the illness with them as well. Is it reasonable? I think you should think twice before you eat too much yes too much fried and BBQ food because frying and barbecuing meat and fish containing proteins creates polycyclic hydrocarbons, such as benzopyrenes, which are also one of the main constituents in cigarette smoke that cause lung cancer. It does not stop there, some people have a fag or two after the meal. That does not mean one should not eat fried food at all but one must take care of themselves by eating in moderation and not so frequently. Your comments are welcomed perera6@hotmail.co.uk